Andromeda

And · genitive Andromedae · northern sky

The Andromeda figure as the IAU defines it, drawn looking south with east to the left — the orientation you see standing outside.

At a glance

Catalogued stars
155
Visible to the eye
155 stars
Brightest star
Alpheratz (2.07)
Best seen
September
Declination span
+23.4° to +48.6°
Nearest star
HD 10307 · 41.5 ly

Visible from everywhere north of about 41°S.

When and where to look for Andromeda

Andromeda crosses the meridian — its highest point in the sky — at local midnight around September, which makes the months from August to October the easiest time to find it in the evening. It spans declinations +23.4° to +48.6°, so visible from everywhere north of about 41°S.

The quickest way to find it is to open the live AR sky map and point your phone at the sky — if Andromeda is above your horizon right now, its figure is drawn in the position it genuinely occupies above you.

Brightest stars in Andromeda

StarMagTypeDistance
Alpheratz21Alp And2.07B9p97 ly
Mirach43Bet And2.07M0IIIvar197.4 ly
Almach57Gam1And2.10B8V393 ly
31Del And3.27K3III...105.5 ly
Nembus51 And3.59K3III177.2 ly
1Omi And3.62B6pv SB686.6 ly

Magnitude runs backwards: lower numbers are brighter, and anything below about 6.5 is beyond the naked eye under a dark sky.

What Andromeda is made of

The catalogue lists 155 stars within Andromeda, of which 155 are magnitude 6.5 or brighter — the limit of what an unaided eye picks up under a genuinely dark sky. The rest need binoculars or a telescope.

Spectral make-up

B30
A26
F26
G22
K46
M5

Spectral class is a temperature ordering, running from O at around 30,000 K down to M below 3,500 K. A constellation is a direction, not a group, so this is simply what happens to lie along that line of sight.

The closest catalogued star in this direction is HD 10307 at 41.5 light years. The most distant is HD 11884 at roughly 2,219 light years — stars that appear side by side here are nothing of the sort.

Deep-sky objects in Andromeda

  • Andromeda Galaxy — galaxy

These are marked on the sky map, so you can see where they sit relative to the constellation figure in real time.

Nearby constellations